spicontrol.c

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/* spicontrol.c - spicontrol */

#include <xinu.h>

/*------------------------------------------------------------------------
 * spicontrol  -  Control function for SPI device
 *------------------------------------------------------------------------
 */
devcall spicontrol (
    struct  dentry  *devptr,    /* Entry in device switch table */
    int32   func,           /* Control function     */
    int32   arg1,           /* Argument 1, if needed    */
    int32   arg2            /* Argument 2, if needed    */
    )
{
    struct  spi_csreg *csrptr;  /* SPI control and status regs  */
    struct  spi_transfer *msg;  /* Message pointer      */
    int i;          /* For loop index       */

    /* Get the pointer to the SPI CSRs */

    csrptr = (struct spi_csreg *)devptr->dvcsr;

    /* Get the pointer to the message */

    msg = (struct spi_transfer *)arg1;

    switch(func) {

     /* This is a SPI transfer */

     case SPI_CTRL_TRANSFER:

        for(i = 0; i < msg->length; i++) {

            /* Wait while the transmit register is not empty */

            while((csrptr->ch[0].chstat & SPI_CHSTAT_TXS) == 0);

            /* Send a byte */

            csrptr->ch[0].chtx = msg->txbuf[i];

            /* Wait until there is a byte in the receive register */

            while((csrptr->ch[0].chstat & SPI_CHSTAT_RXS) == 0);

            /* Read the byte from the receive register */

            msg->rxbuf[i] = csrptr->ch[0].chrx;
        }

        /* End the transfer by changing CS level */

        csrptr->ch[0].chconf &= ~SPI_CHCONF_FORCE;
        csrptr->ch[0].chconf |= SPI_CHCONF_FORCE;

        break;
    }

    return OK;
}